CBSE Class 12 Chemistry 2017 Delhi Set 1 Solved Paper

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Question : 16
Total: 26
Following compounds are given to you :
2-Bromopentane, 2-Bromo-2-methylbutane, 1-Bromopentane
(i) Write the compound which is most reactive towards SN2 reaction.
(ii) Write the compound which is optically active.
(iii) Write the compound which is most reactive towards β-elimination reaction.
Solution:  
(a)
H3CCH2CH2CH2CH2Br
1Bromopentane

(b)
H3CCH2CH2
Br
|
CH
CH3
2Bromopentane

(c)
H3CCH2
Br
|
C
|
CH3
CH3
2Bromo2methylbutane

(i) These figures show that (a) contains the least steric hindrance so towards the SN2 reaction, 1-bromopentane will be the most reactive.
(ii) Figure b of 2-bromopentane has chiral carbon in it. So, it is optically active.
(iii) Towards the β-elimination, 2-bromo-2methylbutane will be the most reactive as it will form most stable alkene (on account of the highest number of α-hydrogens.)
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